How do you import a Compositing Node Set-up?
You can do this by making these nodes into a custom Node Group and then appending it to the file. To do this select all the nodes, and press Ctrl+G. (I would recommend not including the Render Layer and Composite nodes, as they will be present in the new file)

Now you can go to your new file and select File > Append and then navigate to the proper .blend file and then into the NodeGroup folder. Select the desired node group, and click Append.

Now you can go into your node editor and use Shift+A > Group to select your node group. You can edit it using Tab.